Vertical balancing machines are commonly used to test a rotary part for unbalance by rotating the part about a vertical axis and measuring the vibrational forces which occur when the part is not balanced. A motor driven vertical spindle holds the part for rotation and the spindle is mounted on a suspension with a predetermined spring rate so that for a given sprung mass a known resonant frequency is established. The part is driven at a rate much lower than the resonant frequency in the case of a hard suspension or at a rate much higher than the resonant frequency in the case of a soft suspension. The present invention is particularly directed to a hard suspension machine although the principle of the machine can be adapted to a soft suspension.
Where the balancing machine is used as a universal machine, i.e., adapted to process a wide range of different parts, it is useful to replace a suspension or a spindle to provide a drive for a certain class of parts to be balanced. It is also useful, even in special purpose machines, to be able to remove the spindle or the suspension from the machine base for service of the bearings or the like. In addition, the manufacture of such balancing equipment would be facilitated by a structure which features simplicity of assembly. Usually such machines are not constructed in a manner to allow quick and easy removal and replacement. On the other hand, machines of simple structure have been known in the art, for example that shown in U.S. Pat. No. 3,130,587 to Kinsey et al. That patent has a suspension and spindle assembly which is secured as a unit to an apertured horizontal support plate. Only a drive shaft and unbalance pickup means extend through the aperture. The transducers are separate from the unit and are attached directly to the support plate.